Method and device for optical recording and optical record carrier

ABSTRACT

The invention relates to a method and device for forming marks and lands by applying a radiation beam to a recording surface of an optical record carrier. During a recording process a reading power level is set in dependence with a recording power level (recording speed). Additionally, cooling gaps are proposed immediately after the recording pulses. The reading during the recording is carried out only for longer lands. The invention relates to a optical record carrier, where the formula for determining the reading power is contained in the control information.

The invention relates to a method of recording information on an opticalrecord carrier, where optically readable marks are formed on the opticalrecord carrier by recording pulses applied to a recording surface of theoptical record carrier at a recording power level of an irradiationbeam, and where optically readable lands are formed by intervals betweenthe recording pulses at a bias power level of the irradiation beam;where during a recording process the bias power level is set at areading power level to read pre-recorded information written on theoptical record carrier.

The invention also relates to a device for recording information on anoptical recording carrier, comprising: recording means for writing apattern of optically readable marks and lands on the optical recordcarrier by irradiating a recording surface of the optical record carrierwith an irradiation beam; reading means for reading, during a recordingprocess, pre-recorded information written on the optical record carrierand supplying a read signal; processing means for converting inputinformation to be recorded into an output signal supplied to therecording means, the output signal representing the input informationand corresponding to recording pulses and intervals between therecording pulses.

The invention further relates to an optical recording carriersusceptible for forming a pattern of optically readable marks and landsby an irradiation beam, comprising a substrate, control information, aninformation recording area, where the information recording areaincludes pre-recorded information.

A recording method of the kind set forth in the preamble is known fromthe Compact Disc Recordable (CD-R) System Description (also known as theOrange Book). When recording data on the CD-R, a read power level isapplied between recording pulses in order to sample ATIP (absolute timein pre-groove) information for tracking purposes. As specified in theCD-R standard, the read power level is set at 0.7 mW. The nominalconstant linear velocity speed (CLV-speed) of the CD system is between1.2 to 1.4 m/sec. However, the system is also specified to run at higherspeeds, such as, for example, twenty four times the nominal speed (24×).Recording at higher speeds requires that a recording power level forforming marks on a recording surface of the optical record carrier isincreased almost proportionally.

It is a drawback of the known method that if the read power level duringrecording process remains fixed at the 0.7 mW, the dynamic range betweenrecording power level and reading power level becomes very large.

It is an object of the invention to provide a method of opticalrecording of the kind described in the preamble, which offers reduceddynamic range between recording power level and reading power level.

The object is achieved by a method as described in the preamble which ischaracterized in that the reading power level is determined by at leastone of the parameters: the recording power level and recording speed.

It is found that recording power level is substantially linearlydependent on the recording speed. Therefore, according to the invention,the reading power level during the recording process may be determinedas a relative value with respect to the recording power level or anabsolute value with respect to the recording speed. A formula where thereading power level depends on both the recording power level andrecording speed is also possible, e.g. for different overspeed factors.

It is also found that when a linear dependence between the reading powerlevel and the recording power level is applied, then a scaling factorbetween 0.02 to 0.2 of the linear dependence results in the acceptablevalues of the jitter of recorded marks and lands.

For sake of clarity, the power level of an irradiation beam is set atthe recording power level during recording pulses for forming marks,whereas during intervals between the recording pulses (i.e. for forminglands) the power level is set at a bias power level.

Increase in the reading power level results in thermal interferenceeffects (that is, pre-heat and post-heat effect). It was found thatintroducing a cooling gap during intervals between the recording pulses(i.e. setting the bias power level at a cooling power level) immediatelyafter the recording pulse significantly reduces the effects.Additionally, such cooling gaps improve jitter power margins and reducejitter values. After the cooling gaps the bias power level is set at thereading power level in order to read information pre-recorded on thedisc (e.g. ATIP).

The time length of the marks and lands is determined with relation tothe time length of T, a one period of a reference clock in a datasignal. The time length of the shortest marks and lands is determined bya run-length-limited (RRL) code sequence. For the CD system, the RRLcode sequence is the EFM (Eigth to Fourteen Modulation) code sequenceresulting in the shortest marks and lands of the time length of 3T. Forthe recent Blue-ray Disc (BD) system, the shortest marks and lands havetime length of 2T.

In practical applications, reading the ATIP information during intervalsbetween the recording pulses for forming the shortest lands is omitted.Therefore, a preferred embodiment is proposed, where for intervalsbetween the recording pulses for forming the shortest lands the biaspower level is set only at the cooling power level. On the other hand,for intervals for forming longer lands the bias power level is first setat the cooling power level and then at the reading power level.

The device as described in the preamble is, according to the invention,characterized in that the processing means is arranged to determine areading power level of irradiation for reading, during the recordingprocess, the pre-recorded information written on the optical recordcarrier, where the reading power level is determined by at least one ofthe parameters: the recording power level and recording speed.

In a preferred embodiment, the device is equipped with a storage meansfor storing a formula for determining the reading power level independence with at least one of the parameters: the recording powerlevel and recording speed.

The optical record carrier as described in the preamble, according tothe invention, is characterized in that the control information includesa formula for determining a reading power level of the irradiation beamfor reading the pre-recorded information during a recording process,where the reading power level is determined by at least one of theparameters: recording power level and recording speed.

In a preferred embodiment, the pre-recorded information is stored in aperiodic track modulation of the information recording area, and thefrequency of the periodic track modulation is modulated with a digitalposition-information signal (ATIP).

Although the invention is explained by using a CD-R system as anexample, it will be apparent to those skilled in the art that theinvention may also be applied to alternative optical recording systems.

The objects, features and advantages of the invention will be apparentfrom the following, more specific description of embodiments of theinvention as illustrated in accompanying drawings; therein:

FIG. 1 shows a diagram of a control signal for controlling the power ofthe radiation beam for recording marks and lands on the opticalrecording medium.

FIG. 2 also shows, in another embodiment, a diagram of a control signalfor controlling the power of the radiation beam for recording marks andlands on the optical recording medium.

FIG. 3 shows an optical recording device according to the invention

FIG. 4 shows in a plain view an optical recording medium.

FIG. 1 shows a control signal for controlling the power of the radiationbeam for recording marks and lands on the optical recording medium. Therecording process was performed on a cyanine dye type CD-R disc at therecording speed 24×. When the mark is recorded the control signal, andhence the irradiation power level is set at the recording power levelP_(rec) of 34 mW. The reading power level P_(read) during recordingprocess is determined as a fixed value for 24× and equals 6 mW. Thecooling power level P_(cool) is set at 0.1 mW. When the lands are formedthe control signal, and hence bias power level is first set at thecooling power level for a period of time of 1.5 T and then is set at thereading power level.

FIG. 2 also shows a control signal for controlling the power of theradiation beam for recording marks and lands on the optical recordingmedium. The recording process was also performed on a cyanine dye typeCD-R disc at the recording speed 24×. When the mark is recorded thecontrol signal, and hence the irradiation power level is set at therecording power level P_(rec) of 34 mW. The reading power level P_(read)during recording process is determined for 24× as 12% of the recordingpower level, and therefore equals to 4 mW. The cooling power levelP_(cool) is set at 0.1 mW. The CD-R system run-length-limited codesequence is the EFM modulation, and therefore the shortest marks andlands have the time length of 3T. In this embodiment, when the shortestland was to be formed, the bias power level was set only at the coolingpower level, i.e. 0.1 mW. However, if during the recording process thelonger lands were to be formed, then the bias power level was first setat the cooling power level for a period of time of 1.5 T and then, forthe remaining time needed to form desired land, at the reading powerlevel of 4 mW in order to sample ATIP information.

FIG. 3 shows an optical recording device according to the invention forrecording a data signal on the recording surface of a disc-shapedoptical record carrier. The optical record carrier is rotated around itscenter by a motor. A radiation beam is generated by a radiation sourceand focused onto the recording surface by a lens.

The data signal is connected to processing means 60. A current sourcewithin the control means 60 has three outputs A, B and C. Output Aprovides a current which, when fed to the radiation source through acontrol signal, will produce the radiation beam having a write powerlevel P_(rec). Likewise, outputs B and C provide currents resulting inthe reading power level P_(read) and the cooling power level P_(cool),respectively. The current of each output A, B and C can be selected by aswitch-unit within the processing means. The switch-unit is operated bya pattern generator controlled by the data signal. The pattern generatortransforms the data signal into a control signal. The processing meansalso comprise setting means for setting the current of the output B ofthe current source. The current of output B of the current source is setin dependence on the recording power level. The device also comprises areading means for reading the pre-recorded information written on thedisc and supplying the read signal.

FIG. 4 shows an optical recording medium 40 according to the inventionin a plain view. The record carrier has a substrate, controlinformation, an information recording area. The control informationincludes a formula for determining a reading power level of theirradiation beam for reading the pre-recorded information during arecording process. The information recording area includes pre-recordedinformation in the form of a track pattern comprising a spiral groove 41of constant width provided with a spiral wobble.

1. A method of recording information on an optical record carrier, whereoptically readable marks are formed on the optical record carrier byrecording pulses applied to a recording surface of the optical recordcarrier at a recording power level of an irradiation beam, and whereoptically readable lands are formed by intervals between the recordingpulses at a bias power level of the irradiation beam; where during arecording process the bias power level is set at a reading power levelto read pre-recorded information written on the optical record carriercharacterized in that the reading power level is determined by at leastone of the parameters: the recording power level and recording speed. 2.A method as claimed in claim 1, where the reading power level P_(read)is determined by an equation P_(read)=k*P_(rec) where k is amultiplication constant and P_(rec) is the recording power level.
 3. Amethod as claimed in claim 2, where the multiplication constant k is inthe range from 0.02 to 0.2.
 4. A method as claimed in claim 1, where thebias power level of the intervals between the recording pulses is firstset at a cooling power level and then at the reading power level, wherethe cooling power level is below the reading power level.
 5. A method asclaimed in claim 1, where the bias power level of the intervals forforming the shortest lands is set at a cooling power level, and wherethe bias power level of the intervals for forming longer lands is firstset at the cooling power level and then at the reading power level;where time length of the lands, expressed in the time length of oneperiod of a reference clock in a data signal, is determined by arun-length-limited code sequence.
 6. A device for recording informationon an optical recording carrier, comprising: recording means for writinga pattern of optically readable marks and lands on the optical recordcarrier by irradiating a recording surface of the optical record carrierwith an irradiation beam; reading means for reading, during a recordingprocess, pre-recorded information written on the optical record carrierand supplying a read signal; processing means for converting inputinformation to be recorded into an output signal supplied to therecording means, the output signal representing the input informationand corresponding to recording pulses and intervals between therecording pulses; characterized in that the processing means is arrangedto determine a reading power level of irradiation for reading, duringthe recording process, the pre-recorded information written on theoptical record carrier, where the reading power level is determined byat least one of the parameters: the recording power level and recordingspeed.
 7. A device as claimed in claim 6, comprising storage means forstoring a formula for determining the reading power level in dependencewith at least one of the parameters: the recording power level andrecording speed.
 8. A device as claimed in claim 7, where the storagemeans comprises a multiplication constant k such thatP_(read)=k*P_(rec), where P_(rec) is the recording power level andP_(read) is the reading power level.
 9. A device as claimed in claim 8,where the multiplication constant k is in the range from 0.02 to 0.2.10. A device as claimed in claims 6, where the recording means isoperative to first set the bias power level of the intervals between therecording pulses at a cooling power level and then at the reading powerlevel, where the cooling power level is below the reading power level.11. A device as claimed in claims 6, where the recording means isoperative to set the bias power level of the intervals for forming theshortest lands at a cooling power level, and where the recording meansis operative to first set the bias power level of the intervals forforming longer lands at the cooling power level and then at the readingpower level; where time length of the lands, expressed in the timelength of one period of a reference clock in a data signal, isdetermined by a run-length-limited code sequence.
 12. An opticalrecording carrier susceptible for forming a pattern of opticallyreadable marks and lands by an irradiation beam, comprising a substrate,control information, an information recording area, where theinformation recording area includes pre-recorded information,characterized in that the control information includes a formula fordetermining a reading power level of the irradiation beam for readingthe pre-recorded information during a recording process, where thereading power level is determined by at least one of the parameters:recording power level and recording speed.
 13. An optical recordingcarrier as claimed in claim 12, where the pre-recorded information isstored in a periodic track modulation of the information recording area.14. An optical recording carrier as claimed in claim 13, where thefrequency of the periodic track modulation is modulated with a digitalposition-information signal.
 15. An optical recording carrier as claimedin claim 12, where the control information on the substrate comprises amultiplication constant k such that P_(read)=k*P_(rec), where P_(rec) isthe recording power level and P_(read) is the reading power level. 16.An optical recording carrier of claim 15, where the multiplicationconstant k is in the range from 0.02 to 0.2.